The present invention relates to a support for supporting a substrate during processing in a plasma.
An ionized gas or plasma is used in many types of manufacturing processes, including for example, processes for the fabrication of semiconductors and other active or passive electronic devices. For example, plasmas are used in chemical vapor deposition, etching, and ion implantation processes. In a conventional chamber, a gas distributor provides process gas therein, and an RF voltage is applied to a cathode below the substrate while an anode is electrically grounded to energize the gas to form a plasma. However, conventional plasma chambers often do not provide a uniform plasma across the surface of the substrate because of variations in the RF energy across the substrate. For example, in one chamber design, the peripheral portion of the cathode extends circumferentially around the substrate and a relatively thick insulator shield is used to electrically isolate the peripheral cathode portion. However, the insulator shield covering the cathode reduces the RF current between the cathode and the plasma at the periphery of the substrate. The resultant non-uniform plasma across the surface of the substrate can cause the peripheral portion of the substrate to be non-uniformly processed relative to the central portion of the substrate. Plasma processing may also be nonuniform when the cathode does not extend all the way to the peripheral edge of the substrate, as for example in chambers where the cathode has a diameter slightly smaller than that of the substrate. As a result of these effects, the peripheral substrate portion has often reduced yields by as much as 10 to 30%.
Thus, there is a need for a chamber capable of providing a uniform plasma across the substrate surface, and in particular, across the peripheral edge of the substrate. There is also a need for a chamber that allows extending the plasma beyond the peripheral edge of the substrate. There is a further need for a method of processing a substrate that provides consistent processing across the surface of the substrate and especially at the peripheral edge of the substrate.
The present invention satisfies these needs. In one aspect, the present invention comprises a support capable of supporting a substrate in a chamber. The support comprises a dielectric which covers first and second electrodes and has a surface which is adapted to receive the substrate. A voltage supply is adapted to supply an RF bias voltage to the first and second electrodes.
In another aspect of the present invention, a process chamber is capable of processing a substrate in a plasma. The process chamber comprises a gas distributor adapted to introduce process gas in the chamber; a dielectric comprising a first and a second electrode, the dielectric having a receiving surface adapted to receive the substrate; a conductor below the dielectric; a voltage supply adapted to supply a gas energizing voltage to both of the electrodes; and a collar on the conductor.
In another aspect, a method comprises the steps of supporting a substrate in the process chamber, introducing process gas in the process chamber, supplying a voltage to a first electrode to energize the process gas, and supplying a voltage to a second electrode to energize the process gas.
Another method comprises the steps of supporting the substrate on a support in the process chamber, introducing process gas into the process chamber, supplying a voltage to a first electrode to energize the process gas, and supplying a voltage to a second electrode to remove deposits on the support.